Solvent refining and dewaxing process



April 5, 1966 c. R. sUMMERs, JR

SOLVENT REFINING AND DEWAXING PROCESS Filed April 22, 1963 Unite This invention relates to an improved process for manufacturing lubricating oils and more particularly, to a process for continuously solvent refining and dewaxing lubricating oil stocks that affords improved processing fiexibility and efficiency and reduced investment and operating costs.

A variety of process schemes for the manufacture of lubricating oil stocks by solvent refining and solvent dewaxing have been previously proposed. Some of these proposals have been utilized in commercial operations, but none has been entirely satisfactory from the standpoint of operating efiiciency, liexibility and investment and operating costs. In accordance with one such processing scheme, a wide boiling range lubricating oil stock as such is solvent refined and solvent dewaxed to remove aromatic and waxy components. This type of operation is not wholly desirable since the conditions employed in the solvent refining step inherently cannot be optimum for components of heavy, light and intermediate viscosity contained in the wide boiling range oil stock. In accordance with another process scheme, separate, raw lubricating oil stocks having different viscosities and relatively narrow boiling ranges are obtained by vacuu-m fractionation of reduced crude oil and the thus-obtained fractions are thereafter solvent refined and solvent dewaxed in succession in a single solvent refining and dewaxing facility under conditions as close to optimum for the fraction being processed as possible, within the limitations of this scheme. This type of operation, commonly referred to as blocking or blocking through, has certain disadvantages in that considerable storage capacity is required to store the segregated oil fractions between treatments, the segregated oils are exposed to oxygen and various forms of deterioration during such storage, losses in production are suffered during the times in which the operating conditions in the processing unit are varied to suit a change in the oil being refined, considerable off-set oil is produced during changeovers from one oil fraction to another, the optimum solvent composition will not be available to dewax each oil fraction, filtering of microcrystalline wax is made unduly difficult, and the operation lacks flexibility, since a deviation from normal in any one of the process stages for a particular oil fraction may not be revealed in the corresponding finished oil for long periods of time. It has alsor been proposed to solvent refine and solvent dewax lubricating oil stocks that have been segregated as described above in duplicate, parallel facilities, under operating conditions suited to the respective stocks. However, this type of operation is not entirely satisfactory because of the relatively large investment and operating costs involved in the duplication of solvent treating facilities, refrigeration facilities, solvent recovery systems, etc.

In accordance with the present invention, two or more lubricating oil stocks are continuously solvent treated, blended and dewaxed, under conditions especially suited thereto, without intermediate storage of partly refined oils and all the disadvantages attendant thereto, and without signicanly increasing plant investment and operating costs, In a broad sense, the process of the present invention involves concurrently solvent refining at least two hydrocarbon lubricating oil fractions having dierent viscosities. The oil fractions to be so treated can be obtained by States Patent O fractionation of a hydrocarbon oil having a viscosity in the lubricating oil range and having a relatively wide boiling range 'into two or more lubricating oil fractions or cuts having different viscosities and relatively narrower boiling ranges. Alternatively, the separate fractions may be obtained from two or more different raw oil stocks, The thus-obtained, several oil fractions are concurrently solvent refined with a solvent capable of preferentially dissolving aromatic-type hydrocarbon components of the oil, in separate treating Zones, and under conditions especially suited to the nature of the oil fractions being processed. An example of a preferred solvent refining solvent is furfural, but other equivalent solvents can be used. When one of the aforesaid lubricating oil cuts or fractions is a residual fraction and contains asphaltic components, such fraction is advantageously subjected to a deasphalting treatment prior to solvent refining, so as to avoid int-roducing these components into the solvent refining treating stage. Excellent results are obtainable with liquefied propane as the deasphalting solvent, but other liquefied, low molecular weight hydrocarbons can also be used. After separation of the solvent and extract phases obtained from the individual solvent refining zones, the separately obtained extract phases, containing the bull; of the selective solvent, are combined, as are the separately obtained rafiinate phases, and solvent is concurrently separated and recovered, usually by distillation, from the combined extract phase and the combined raffinate phase, in separate solvent recovery zones. The combined rafnate, a partly refined, wide boiling range mixture of oils, is then solvent dewaxed under conditions especially suited to the blend being treated with a solvent having a high solvency for the oily components of the mixture under conditions effective to precipitate waxy components of the mixture. An example of a preferred dewaxing solvent is a mixture of toluene-methyl ethyl ketone, but good results are also obtainable with other equivalent dewaxing solvents. Precipitated wax is removed from the treated mixture by filtration, and dewaxing solvent is then separated from dissolved oil and recovered for reuse. The solvent-free oily residue is a solvent refined, solvent dewaxed, wide boiling range mixture of oils. The abovedescribed process scheme is especially advantageous when followed by a suitable finishing treatment carried out on the solvent refined and dewaxed oil mixture to decolorize the same and otherwise to improve the product quality, and by a subsequent refractionation to form two or more separate, finished lubricating oil fractions having different viscosity characteristics. The preferred finishing operation is hydrofinishing, i.e., a relatively mild, saturative, catalytic hydrogenation, but other conventional finishing treatments, for example, clay filtration, can be used.

Referring now briefly to the single figure of drawing, there is shown a simplified flow diagram of a lubricating oil plant embodying the process scheme of this invention. The invention can probably be best understood by more particular reference to the drawing. ln the drawing, numeral 4 designates a primary vacuum distillation tower for separating a relatively wide boiling range hydrocarbon oil into two or more lubricating oil fractions having appreciably different viscosities and having relatively narrower boiling ranges. Numeral 17 denotes a solvent deasphalting unit for precipitating the asphaltic components of the oil residue obtained from vacuum tower 4. Numerals 28, 30 and 32 denote separate solvent extraction units for preferentially dissolving out aromatic-type hydrocarbon components from the respective cuts or fractions obtained from vacuum tower 4. Numeral 59 denotes a solvent dewaxing unit for preferentially dissolving the oily components of the mixed rafiinates obtained from units 28, 30 and 32, and at the same time rejecting the waxy components. Numeral 70 refers to a finishing vessel for preferentially reducing one or more of the resinous, asphaltic, carbonaceous and/ or sulfur constituents of the mixed, dewaxed raffinate, and numeral 74 indicates a second vacuum distillation tower for refractionating the combined, dewaxed reftinate into the separate lubricating oil fractions having the desired viscosities.

In operation, a relatively wide boiling range hydrocarbon oil containing two or more component oils of lubrieating viscosity, for example, a residual oil obtained by atmospheric distillation of a crude petroleum oil, is introduced by way of line 2 into vacuum tower 4 for fractional distillation under reduced pressure in conventional manner into two or more lubricating oil fractions of relatively narrower boiling range and having appreciably different viscosities.

The wide boiling range hydrocarbon oils referred to above can comprise not only the reduced crude oils or long residues that remain after distillation of a crude petroleum oil under substantially atmospheric pressure to remove all of the components that can be vaporized at temperatures below those at which cracking occurs, but also they can comprise short residues or residual oils remaining after vacuum distillation of long residues to remove lighter components, or alternatively, they can comprise long lubricating oil distillate fractions, that is, oil fractions having a viscosity in the range of lubricating oils and that are sufficiently wide boiling as to be capable of forming two or more different boiling range oil fractions of appreciably different viscosities. The expression lubricating oil viscosities, or equivalent expressions, are used herein in their normal sense to mean viscosities of at least about 40 SUS at 100 F. or higher. Examples of lubricating oil fractions into which the above-mentioned wide boiling range lubricating oil stocks can be separated include neutral oils, light, medium and heavy lubricating oil distillates, and cylinder stocks, that is, the residual oil fraction that cannot be further vaporized at the reduced pressure prevalent in the vacuum distillation tower without cracking.

Referring again to the drawing, the overhead from vacuum tower 4, a gas oil of less than lubricating oil viscosity but suitable for use as a catalytic cracking stock, is removed by way of line 6. A light lubricating distillate is removed as a side stream from vacuum tower 4 by way of line 8, and medium and heavy lubricating distillates are separately removed as higher boiling side streams from tower 4 by way of lines 10 and 12, respectively. The unvaporized residue obtained from the vacuum distillation carried out in tower 4 is removed from the tower by way of line 14. A portion of the residue removed through line 14 is withdrawn from the system by way of lines 13 and 20 for use as heavy fuel oil. Another portion of the residue from line 14, suicient to produce the desired amount of finished bright stock, is withdrawn from line 14 through line 16 and introduced into a solvent deasphalting treating stage, here a propane deasphalting zone. The deasphalting solvent is preferably liquid propane, but other liquitied, normally gaseous hydrocarbons such as methane, ethane, and butane can be used. Aliphatic alcohols such as ethyl, butyl, amyl and hexyl alcohols also can be used. The solvent:oil ratios and deasphalting conditions will vary `in known fashion in accordance with the solvent and the oil being treated. By way of illustration, when the deasphalting solvent is propane, solvent ratios in the range of about 2:1 to 10:1 4and deasphalting temperatures in the range of about 100 to 180 F. can be used. Pressures of the order of 200 p.s.i.g. or more are required in the deasphalting zone in order to maintain the light hydrocarbon deasphalting solvents in liquitied form.

Precipitated asphalt is removed from deasphalting zone 17 by way of line 22. Propane is recovered from the precipitated asphalt by dashing and stripping in zone 23. Evaporated propane is recovered by way of line 27 for compression, reliquetication and recycling to zone 17. Precipitated asphalt free of propane is withdrawn from zone 23 through line 25 from which it is introduced into line 20 to form, together with the untreated residue from tower 4, a heavy fuel oil stream. The propane solution of deasphalted oil is removed from zone 17 by way of line 26, from which it is introduced into solvent flashing and stripping zone 31. Evaporated propane is recovered by way of line 29 for compression, reliquefication and recycling to zone 17. Deasphalted oil is removed from Zone 31 by way of line 33.

After separation of the relatively wide boiling range hydrocarbon oil of lubricating viscosity into separate fractions having appreciably different viscosities, and after deasphalting of the asphaltic residue, the particular i crude oil stock utilized in the specic embodiment described hereinafter, the optimum solvent refining conditions and solventzoil ratios for these two fractions are closely similar. When this is not the case the medium lubricating distillate will be solvent refined in a separate vessel, not shown, connected in the system similarly as vessels 2S, 30 and 32.

To continue, the combined side streams from lines 8 and 10 are introduced into solvent extraction zone 28,

the heavy lubricating distillate side stream from line 12 is introduced into solvent extraction zone 30, and the deasphalted residual oil from deasphalting zone 17 is introduced into solvent extraction yzone 32 for concurrent solvent extraction treatment under conditions especially suited to the nature of the respective oil fractions being processed. The solvent:oil ratios and/or the conditions under which solvent extraction is carried out will normally differ in the respective solvent treating stages because the optimum treating conditions for each oil will normally differ.

It is important for purposes of the present invention that the individual fractions of appreciably differing viscosities be treated separately in separate solvent extraction zones, since treatment of a single, wide boiling range lubricating oil stock witha single thus-segregated lubricating oil fractions are in condition for concurrent extractive treatment in separate treating zones with a solvent capable of preferentially dissolving aromatic-type hydrocarbons. The solvent used in the separate solvent refining zones is advantageously furfural, but phenol or Iother equivalent solvents can be used. Examples of such other solvents are beta,betadichlorodiethyl ether (Chlorex), nitrobenzene, propane-cresylic acid, sulfur dioxide, and sulfur dioxide-benzoltraction conditions will vary in conventional manner, in

accordance with the particular solvent chosen and in aci cordance with the nature of the oil subjected to extrac-` tion. For purposes of illustration, it may be noted that when the solvent is furfural, the solvent:oil ratios will i normally vary between about 1:1 and about 5:1 andthe extraction will be carried out at temperatures in the range of about 100 to 300 F., the particular extraction temperature and solventzoil ratio being selected and adjusted to suit the particular oil fraction being treated and to yield a finished oil having the desired properties.

In the embodiment illustrated in the drawing, the light lubricating distillate side stream from line 8 and the medium lubricating distillate side stream from line 10 are shown as being combined, because for lthe solventzoil ratio and under a single set of treating conditions will result either in over-treatment of the lighter components of the oil or under-treatment of the heavier components of the oil, or both. It is also important for purposes of i the present invention that the respective lubricating oil fractions prepared as described above be 4treated concuri rently in parallel treating zones to avoid any necessity for intermediate storage of the respective fractions, and

thereby to avoid the diiculties associated therewith.

The solvent extract phases from each of solvent extraction zones 28, 30 and 32 are withdrawn respectively i The solventroil ratios and the exi through lines 52, 54 and 56, and combined in line 58, from which they -are introduced by way of line 60 into extract stripper 62. In vessel 62, furfural is removed from the extract by differential evaporation and recovered in line 64 for recycling to the previously discussed solvent extraction zones. The solvent-free extract obtained from stripper 62 is removed by way of line 63 and introduced into the heavy fuel oil stream flowing through line 20.

The raffinate phase is removed from each of solvent extraction zones 28, 30 and 32 by way of overhead lines 34, 36 Iand 38, respectively. The raffinate from line 38 and from line 36 are combined in line 42 and this combined rainate is further combined with the rafiinate stream from line 34 in line 44, and the total combined raflinate from the three solvent extraction zones is introduced int-o rainate stripper 46. The furfural contained in vthe raffinate is removed therefrom by stripping `and is recovered vby way of line 48 for recycling to the solvent extraction zones. The solvent-free, `combined rafiinate is removed from line 46 -by way of line S0, from where it passes into solvent dewaxing zone 59.

The combination of the extract and raffinate phases from the respective solvent extraction zones prior to recovery of solvent therefrom is important for purposes of the present invention, since this expedient avoid-s duplication of rel-atively costly, solvent recovery equipment. Thus, by virtue of ythe separate solvent extraction zones and the combined raffinate and extract stripping zones, I am able to obtain the advantages of separate, concurrent solvent extraction at very little greater equipment cost than would be entailed by a single Isolvent extraction tre-ating stage of a volume equivalent to the three vessels utilized in the illustrated embodiment. The combination of the rafinate streams for recovery of solvent in a single zone is made possible by the fact that the next subsequent treating step in the herein-disclosed processing scheme is solvent dewaxing. Unlike the solvent extraction treatment which can only be carried out on la wide boiling r-ange lubricating oil fraction at the cost of over-treating some portions and/or under-treating other portions of such fraction, solvent dewaxing can be carried out on a wide boiling range lubricating oil fraction using a single solvent mixing facility and a single chilling facility, at the optimum conditions for that fraction, Without sacrifice in oper-ating efiiciency, product quality -or the like. In fact, operating efficiency and product quality are actually improved by effecting solvent dewaxing on the c-ombined raffinate stream from the solvent extraction zones, as compared'with blocked-through operation, since the optimum solvent composition, solventzoil ratio and extraction temperature for the combined fraction can be utilized. In contrast, in blocked-through operation, it is impractical to vary the s-olvent composition during successive treatment of the respective fractions .blocked through the dewaxing treatment, because of the extra equipment costs that would be necessary to separate the dewaxing solvent mixture into its components. Accordingly, the solvent composition in blocked-through operations can never be optimum for more than one of the fractions beingsubjected to treatment, and possibly Will not be optimum for any of these fractions.

The solvent 'employed in the dewaxing operation is 'advantageously an aromatic hydrocarbon-ketone mixture such as benzene and/ or toluene and methyl ethyl ketone, but other ketones such as acetone or methyl lbutyl ketone can `be used. For example, solvent mixtures containing 30 to 60 percent methyl ethyl ketone, 10 to 25 percent toluene and 40 Ito 60 percent benzene can be used to advantage. Alternatively, other dewaxing solvents such as propane can be employed. Similarly, as in the case of the solvent extraction treatment referred to above, the optimum solvent:oil ratios, the solvent composition and the dewaxing conditions will be determined by the nature of the solvents and the oils subjected to the dewaxing treatment. By Way of illustration, when the solvent is an aromatic hydrocarbon-ketone mixture, solventzoil ratios in the range of about 1:1 to 4:1 and dewaxing temperatures in the range of about 30 -to 50 F. can be used. The temperatures referred to here are the temperatures utilized in chilling a solution of the solvent refined, combined raffinate, so as to precipitate Wax. `It will be understood that the solution subjected to chilling is first formed at a higher temperature, sufficient to effect dissolution of all or substantially all of the combined rafinate product. In each of the solvent dewaxing processes referred to, `solvent is normally separated and recovered from the -dewaxed oil by some form of differential vaporization. Such differential vaporization will usually be effected yby heating the solvent-containing material and may also be accompanied by a reduction in pressure and/ or by the use of stripping agents such as steam, if desired.

The chilled oil and dewaxing solvent solution obtained in dewaxing zone 59, containing precipitated wax, is filtered through suitable wax filtering means, not shown, for example a continuous drum filter, and a slack Wax containing some dewaxing solvent is removed from the dewaxing zone 59 by way of line 68 and transferred to solvent flash `and stripping zone 69, where entrained solvent is separated from slack wax by differential evaporation and recovered through line 71 for recycling to dewaxing zone S9. Wax filtration is facilitated in the presently disclosed process scheme, as compared with separately dewaxing two or more oil fractions, by virtue of the fact that the difiiculty flterable, microcrystalline wax is filtered together with crystalline wax. Solventfree slack Wax is removed from stripping zone 69 by Way of line '73. A solution of dewaxed oil in dewaxing solvent is removed from treating zone 59 by way of line 75 and thereafter introduced into solvent fiash and stripping zone where solvent is separated from dewaxed oil by differential evaporation. Evaporated solvent is recovered through line 67 for recycling to dewaxing zone 59. Solvent-free dewaxed oil is removed from stripping zone 65 by way of line 66 and then introduced into finishing zone '70.

As `,indicated previously, the finishing treatment effected in zone '70 can Vbe any operation adapted to decolorize the oil and/or to reduce one or more of the resinous, asphaltic sulfur and carbonaceous components of the solvent treated and dewaxed oil, and thereby to improve the color Vstability and carbon residue of the oil. In the preferred embodiment, the finishing treatment is a hydrofinishing treatment, that is, a relatively mild, saturative, catalytic hydrogenati-on treatment of the kind described in detail in U.S. Patent No. 2,953,519, and/or of the kind illustrated in the Oil and Gas Journal, dated August 14, 1961, at page 116. However, the invention is not limited to hydrofinishing, and other finishing treatments can be used. For example, there can be used an acid-treating and clay ltration finishing treatment, utilizing clays normally used in clay finishing such as fullers earth, bauxite and Filtrol that have been activated for filtering and decolorizing purposes by roasting at temperatures of the order of 400 to 900 F. The temperatures, pressures and space velocities employed in hydrofnishing, or alternatively, the temperatures, treating times, and oilzclay ratios utilized in clay finishing will vary in known manner, depending upon the nature of the oil subjected to the finishing treatment and also in accordance with the properties desired in the finished oils. By way of illustration, when the finishing operation employed is hydrofinishing, pressures between about 500 and about 10,000 p.s.i., preferably between about 500 and 2,500 p.s.i., temperatures in the range of 450 to 825 F., preferably 450 to 700 F., and space velocities between about 0.2 and 8 Will be employed. Hydrogen is generally employed in amounts of between about 500 and 10,000 s.c.f./bbl. of hydrocarbon oil charge stock.

Upon completion of the finishing treatment, finished oil is removed from finishing vessel 70 by way of line 72 and then introduced into vacuum distillation tower 74. Gas, gas oil, and finished lubricating oil fractions of different viscosities are then removed by side streams from tower 74. A finished bright stock fraction is removed as a residue by way of line 84.

The fractionation of the combined finishing and dewaxed raffinate stream in tower 74 is important for purposes of the present invention, as compared with blockedthrough operation, as the production of a variety of lubricating oil fractions of appreciably different viscosities and the fiexibility of control over the properties of these lubricating oil fractions is facilitated thereby. It will also be understood that the quality of the products produced in the manner described will be superior to that of products of corresponding viscosity produced by blending of finished lubricating oil stocks prepared by blocked-through operation. Thus, a finished lubricating oil of a given viscosity that is obtained by blending of a lighter and heavier cut will not contain molecules of the same size and will not be of identical quality as a lubricating oil cut having the same viscosity obtained by distillation from a mixture of the same lighter and heavier finished lubricating oil stocks.

ln a specific embodiment, a long, residual oil obtained by atmospheric distillation of a crude petroleum oil is separated by vacuum distillation into a gas oil overhead, 11.0 percent by volume of the crude oil of a light lubricating distillate having a viscosity of about 100 SUS at 100 F., 9.7 percent by volume of the crude oil ofva medium lubricating oil distillate having a viscosity of about 400 SUS at 100 F., 5.2 percent by volume of a heavy lubricating oil distillate having a viscosity of about 100 SUS at 210 F., and 22.0 percent by volume of the crude oil of a residue containing asphaltic components. This residue is introduced into a propane deasphalting vessel for contact with liquefied propane at a tower pressure of about 500 p.s.i.g. and at an average tower temperature of about 131 F., utilizing a propanezoil ratio of about 8: 1. The solvent-free deasphalted oil, comprising about 6.93 percent by volume of the crude oil, is introduced into a furfural extraction zone, where it is contacted with furfural in the proportion of about 3.5 volumes of furfural per volume of deasphalted oil and at an average tower temperature of about 248 F. The raffinate obtained from this step after solvent removal amounts to about 4.23 percent by volume of the crude oil. t

Concurrently with the solvent extraction of the deasphalted residual oil, the combined light and medium lubricating oil distillates referred to above and the heavy lubricating oil distillate also referred to above are subjected to furfural extraction in separate solvent extraction zones. The light and medium lubricating oil fractions can be combined in this instance, since the optimum solvent refining temperature and solvent:oil ratios for the respective stocks differ only slightly. The combined light and medium lubricating oil distillates are extracted using a furfural to oil ratio of about 1,8:1 and an average extraction temperature of about 193 F. to produce a solvent-free raffinate amounting to about 12.5 percent by volume of the crude oil. The heavy lubricating oil distillate is extracted with furfural using a solventzoil ratio of about 2.911 and using an average extraction temperature of about 208 F., to produce a solvent-free raffinate amounting to about 2.55 percent by volume of the crude oil.

The combined, solvent-free raflinates obtained from the separate solvent extraction zones, consisting of about 19.2 percent by volume of the crude oil is introduced to a solvent dewaxing zone. Solvent dewaxing is effected with a lzlbyvolume mixture of methyl ethyl ketone and toluene, using a solvent:oil ratio of about 4:1, and a dewaxing temperature of about 15 F. The solvent-free, dewaxed raffinate, consisting of about 15.54 percent by waxed raffinate charge stock. The finished oil .is then vacuum distilled under conventional conditions to obtain` a light lubricating oil distillate having a viscosity ofl about SUS at 100 F., comprising about 9.2 percentI by volume of the vacuum tower charge, a medium lubricating oil distillate having a viscosity of about.250 SUS at 100 F. and comprising about 32 percent by volume of the vacuum tower charge, a heavy lubricating oil dis? tillate having a viscosity of about 600 SUS at 100 F. and comprising about 32.3 percent by volume of the vacuum tower charge stock, and a bright stock having a `viscosity of about SUS at 210 F. and comprising about 24.5.`

percent by volume of the vacuum tower charge, stock.

It will be understood that the invention is not limited to the particular deasphalting, solvent extraction, solvent dewaxing and finishing processes utilized in the specific embodimentV and that other such-processing treatmentsl disclosed herein can be utilized with appropriate adjustment of treating conditionsysolvent ratios and the like.

Numerous other modifications of the invention will readily suggest themselves to those skilled in the art, and these modifications can be resorted to without departure from the spirit or scope of the invention. Accordingly, I do not intendto be limited to the embodiments disclosed herein but only by the scope of the claims appended hereto.

I claim:

1. A process comprising concurrently solvent refining at least two hydrocarbon lubricating oil fractions of different viscosities with a solvent effective preferentially to dissolve aromatic hydrocarbon components of said lubricating oil fractions, in separate treating zone, and under conditions especially suited to the individual lubricating oil fractions, separating the extract and raffinate phases obtained in each such zone, combining the rafiinates fromsaid zones, separating solvent from the combined rafiinates, solvent dewaxing the combined raffinate with a solvent effective preferentially to dissolve the oily components of said combined rafnate under conditions effec# tive to precipitate waxy components, such conditions being especially suited to the nature of such combined raffinate, separating precipitated wax from dewaxed oil and solvent, and separating dewaxing solvent from dewaxed oil.

2. The process of claim lwhere the solvent refining solvent is furfural and the dewaxing solvent is a mixture of methyl ethyl ketone and at least one aromatic hydrocarbon selected from the groupy consisting of benzene and toluene. n

3. A process 4comprising concurrently solvent refining at least two hydrocarbon lubricating oil fractions of different viscosities with a solvent effective preferentially to dissolve aromatic hydrocarbon components of said lubricating oil fractions, in separate treating zones, and

under conditions especially suited to the individual lubri-` cating oil fractions, separating the extract and raffinate phases obtained in each suchzone, combining the raffinates from said' zones, combining theextract obtained from said zones, separatingsolvent from the combined rafinates, separating solventfrom the combined extract, solvent dewaxing the combined raffinate with a solvent effectivev preferentially to Vdissolve the oily components of said combined raffinate, under conditions effective to` precipitate waxy components, such conditions being especially suited to the nature of such combined raffinate,

separating precipitated wax from dewaxed oil and solvent, andseparating dewaxing solvent froml dewaxed oil.

4. A process comprising concurrently solvent refining at least two hydrocarbon lubricating oil fractions of different viscosities with a solvent effective preferentially to dissolve aromatic hydrocarbon components of said lubrieating oil fractions, in separate treating zones, and under conditions especially suited to the individual lubricating oil fractions, separating the extract and raffinate phases obtained in each such zone, combining the raffinates from said Zones, separating solvent from the combined raffinates, solvent dewaxing the combined raffinate with a solvent effective preferentially to dissolve the oil components of said combined raffinate, under conditions effective to precipitate waxy components, such conditions being especially suited to the nature of such combined raffinate, separating precipitated wax from dewaxed oil and solvent, separating dewaxing solvent from dewaxed oil, and subjecting the dewaxed oil to a finishing treatment to improve the color thereof.

5. A process comprising concurrently solvent refining at least two hydrocarbon lubricating oil fractions of different viscosities with a solvent effective preferentially to dissolve aromatic hydrocarbon components of said lubricating oil fractions, in separate treating zones, and under conditions particularly suited to the individual lubricating oil fractions, separating the extract and raffinate phases obtained in each such zone, combining the raffinates from said zones, separating solvent from the combined raffinates, solvent dewaxing the combined raffinate with a solvent effective preferentially to dissolve the oily components of said combined raffinate, under conditions effective to precipitate waxy components, such conditions being especially suited to the nature -of the combined raffinate, separating precipitated wax from dewaxed oil and solvent, separating dewaxing solvent yfrom dewaxed oil, subjecting the dewaxed oil to a finishing treatment to remove color-forming components therefrom and to improve the carbon residue of the dewaxed oil, and fractionating the finished, dewaxed oil to form at least two finished lubricating oil fractions of different viscosities,

6. The process of claim where said finishing treatment is hydroiinishing.

7. A process comprising fractionating a wide boiling range hydrocarbon oil, at least a portion of which has a viscosity in the lubricating range, into at least two lubricating oil fractions having different viscosities, one of said fractions being a distillate fraction and the other of which 'being a residual fraction containing asphaltic components, solvent deasphalting the residual fraction with a solvent effective to precipitate asphaltic components from the oil, separating precipitated asphalt from deasphalted oil and deasphalting solvent, separating deasphalting solvent from deasphalted oil, thereafter concurrently solvent refining the thus-obtained deasphalted oil fraction and said distallate fraction with a solvent effective preferentially to dissolve aromatic hydrocarbon components from said lubricating oil fractions, in separate treating zones, and under conditions especially suited to the individual lubricating oil fractions, separating the extract and raffinate phases obtained in each such zone, combining the raffnates from said zones, combining the extract obtained from said zones, concurrently separating solvent from the combined raffinite and from the combined extract in separate solvent recovery zones, solvent dewaxing the combined raffinate with a solvent effective preferentially to dissolve the oily components of said combined raffinate, under conditions effective to precipitate waxy components, such conditions being especially suited to the nature of the combined raffinate, separating precipitated wax from dewaxed oil and solvent, and separating dewaxing solvent from dewaxed oil.

8. The process of claim 7 where the deasphalting solvent is propane.

9. A process comprising fractionating a wide boiling range hydrocarbon oil, at least a portion of which has a viscosity in the lubricating range, into at least two lubricating oil fractions having different viscosities, one of said fractions being a distillate fraction and the other of which being a residual fraction containing asphaltic components, solvent deasphalting the residual fraction with a solvent effective to precipitate asphaltic components from the oil, separating precipitated asphalt from deasphalted oil and deasphalting solvent, separating deasphalting solvent from deasphalted oil, thereafter concurrently solvent refining the thus-obtained deasphalted oil fraction and said distillate fraction with a solvent effective preferentially to dissolve aromatic hydrocarbon components from said lubricating oil fractions, in separate treating zones, and under conditions especially suited to the individual lubricating oil fractions, separating the extract and raffinate phases obtained in each such zone, combining the raffinates lfrom said zones, combining the extract obtained from said Zones, concurrently separating solvent fram the combined raffinate and from the combined extract in separate solvent recovery zones, solvent dewaxing the combined raffinate with a solvent effective preferentially to dissolve the oily components of said combined raffinate, under conditions effective to precipitate waxy components, such conditions being especially suited to the nature of the combined raffinate, separating precipitated wax from dewaxed oil and solvent, separating dewaxing solvent from dewaxed oil, and subjecting the solvent-free dewaxed oil to a finishing treatment to improve the color thereof.

10. A process c-omprising fractionating a wide boiling range hydrocarbon oil, at least a portion of which has a viscosity in the lubricating range, into at least two lubricating oil fractions, one of said fractions being a distillate fraction and the other `of which being a residual fraction containing asphaltic components, solvent deasphalting the residual fraction with liquefied propane under conditions effective to precipitate asphaltic components from the oil, separating precipitated asphalt from the deasphalted oil solution, separating propane from precipitated asphalt, separating propane from deasphalted oil, thereafter concurrently solvent refining the thus-obtained deasphalted oil and said distillate oil fraction with furfural in separate treating zones under conditions effective to promote preferential dissolution of aromatic hydrocarbon components in the furfural, combining the raffinates from said solvent refining zones, combining the extracts obtained from said zones, concurrently separating furfural from the combined raffiinate and from the combined extract in separate solvent recovery zones, solvent dewaxing the combined raffinate with a mixture of methyl ethyl ketone and at least one aromatic solvent selected from the group consisting of benzene and toluene under conditions effective to precipitate waxy components from the oil, said conditions being particularly suited to the nature of the combined raffinate fraction, separating precipitated wax from dewaxed oil, separating dewaxing solvent from dewaxed oil, subjecting the solvent-free dewaxed oil to a hydrofinishing treatment to improve the color thereof, and fractionating the hydrofinished, dewaxed oil to form at least two finished lubricating oil fractions of different viscosities.

References Cited by the Examiner UNITED STATES PATENTS 2,682,523 6/1954 Talley et al 208-27 2,726,990 12/1955 Baker 208-36 2,761,814 9/1956 Post 208-36 2,780,581 2/1957 Macke et al. 208-36 2,967,146 1/1961 Manley 208-18 DANIEL E. WYMAN, Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner.

H. LEVINE, P. E. KONOPKA, Assslanl Examiners. 

1. A PROCESS COMPRISING CONCURRENTLY SOLVENT REFINING AT LEAST TWO HYDROCARBON LUBRICATING OIL FRACTIONS OF DIFFERENT VISCOSITIES WITH A SOLVENT EFFECTIVE PREFERENTIALLY TO DISSOLVE AROMATIC HYDROCARBON COMPONENTS OF SAID LUBRICATING OIL FRACTIONS, IN SEPARATE TREATING ZONE, AND UNDER CONDITIONS ESPECIALLY SUITED TO THE INDIVIDUAL LUBRICATING OIL FRACTIONS, SEPARATING THE EXTRACT, AND RAFFINATE PHASES OBTAINED IN EACH SUCH ZONE, COMBINING THE RAFFINATES FROM SAID ZONES, SEPARATING SOLVENT FROM THE COMBINED RAFFINATES, SOLVENT DEWAXING THE COMBINED RAFFINATE WITH A SOLVENT EFFECTIVE PREFERENTIALLY TO DISSOLVE THE OILY COMPONENTS OF SAID COMBINED RAFFINATE UNDER CONDITIONS EFFECTIVE TO PRECIPITATE WAXY COMPONENTS, SUCH CONDITIONS BEING ESPECIALLY SUITED TO THE NATURE OF SUCH COMBINED RAFFINATE, SEPARATING PRECIPITATED WAX FROM DEWAXED OIL AND SOLVENT, AND SEPARATING DEWAXING SOLVENT FROM DEWAXED OIL. 